Method of producing formate of potassium from potassium sulphate and calcium formateor mixtures of constituents adapted to form the latter by way of reaction



Patented Dec. 12, 1933 UNITED STATES PATENT- OFFICE;

Emil Hene, Berlin-Grunewald, Germany, assignor to Rudolph Koepp & Co. Chem. Fabrik A. G. Ocstrich, Rheingau, Germany; a German Com- No Drawing. Application October 20, 1930,

Serial No. 490,104, and'in-Germany November 7 My invention relates potassium formate. I} V It is a well known fact that potassium formate can be producedfrom alkali-earthformates and potassium sulphate. In practice, however, it was impossible up to now to accomplish this conversion quantitatively without the addition of other chemical-agents. j

According to the known methods the conversion or reaction of calcium formate with sodium sulphate gives yields'only a little above 80 per cent; the yield is still less satisfactory if the reaction is carried out with potassium sulphate.

After'much study and research 'I have" discovered the cause of the unsatisfactory conversion and yield, and subsequently I have found away of carrying out the reaction or conversion in a new manner and with the result of a practically quantitative yield and without using any additional agents.

I have found, that in any aqueous solution which contains calcium, potassium, a sulphate residue and a formate residue under certain conditions an equilibrium is formed which does not involve the formation of 'gypsum'as precipitate but leads to the precipitation of syngenite, containing K2SO4+CaSO4.

This equilibrium can be obtained if aqueous solution containing 40 to 70% potassium formate and 60 to 30% of calcium formate respectively react with potassium sulphate, which reaction leads to the formation of syngenite.

The syngenite on the other hand reacts with formate of calcium so as tobring about con- 5- versions resulting in the production of a solution of potassium formate and calcium formate while almost pure gypsum will be precipitated.

This new observation may be utilized in all cases in which it is desired to produce in a simple and inexpensive manner practically quantitative conversions and yields of potassium formate, without the application of any auxiliary agents as hitherto employed.

For instance, I start with the preparation of an aqueous solution of potassium formate and calcium formate to the manufacture .of

2 Claims. (Cl. 250-113 V of potassium, whereupon I separate the clear solution from the insoluble precipitate of syngenite. 2 sKcooH-+ca cooH)z+2K2so K SO CaSO syngenite ;The syngenite is mixed with a pure solution of 5KCOOH+ calcium formate in a vessel provided with a stir-- rer;,the stirrer being put in motion the syngenite is then decomposed and a solution is produced containing potassium formate and calcium formate, the precipitate now consisting substantially of pure, gypsum,

solution containing potassium formate and ca.1-

cium formate.

Example I 500 litres of an aqueous solution containing 7 130 kg. of formate of calcium are mixed in a suitable'vessel provided with a stirrer, with 117 kg. of crude sulphate of potassium containing 90 per cent of pure sulphate of potassium, whereupon the stirrer isput in motion for about one hour. Subsequently the liquor is separated from the precipitate by way of filtration and the latter is subjected to a washing treatment. The 'recovered liquor or solution amounts to about 500 litres containing about 100 kg. of potassium formate and 52 kg. of calcium formate.

The solution produced in this manner is mixed with 195 kg. of potassium sulphate and stirred for about one hour at a temperature of 30 to 40 C., whereupon the liquor is again separated from the sediment by filtration and the latter is washed free of soluble salts. The recoverable solution amounting to about 500 litres will contain approximately 160 kg. of formate of potassium. The recovered sediment or precipitate consisting of syngenite is mixed with 500 litres of the same solutionof calcium formate and stirred as hereinbefore described with the result, that a substance will be separated out by precipitation, which is practically pure gypsum and the solution or liquid to be separated therefrom by filtration,

will contain 52 kg. of calcium formate and 100 kg.

of potassium formate approximately in 500 litres. Example II In a suitable vessel such as anautoclave 1000 litres of milk of lime are mixed withabout .56 kg. of caustic lime and 120 kg. of 'sulph'ate'of potassium and subsequently treated in the usual'manner with carbon monoxide at a raisedpressure and at an elevated temperature. The treatment of the mixture is continued until practically all free lime is bound or converted. Subsequently the resulting solution containing'potassium formate and calcium formate, is separated from the precipitated gypsum by filtration.

The clear solution thus prepared is nowmixed in a vessel provided with a stirrer with about 180 kg. of sulphate offpotassium and thesti'rrer is 'put in motion for "a sufiicient length "of time 'to ensure complete reaction. The-mixture isinow purpose of recovering a pure solution of formate of potassium.

When the precipitates are washed carefully,

the yield of formate of potassium will come up to about 95 per cent. potassium produced in accordance with the pres- :ent invention contain only small proportions of The solutions of formate of calcium compounds-which may be removed by evaporation or precipitation and subsequent filtration.

What I claim is:

l. Aprocess-forthe manufacture of potassium .formate consisting in causing an aqueous solution of calcium formate to react with potassium sulphate in suchproportions, that the filtered solution contains 40 to 70% potassium formate and respectively to 30% calcium forinate,

causing this solution to react with sulphate of potassium so as to form'syngenite, separating the latter 'from the solution of potassium formate,

treating the same with an aqueous solution of calcium formate and separating the solution from theprecipitated ypsum.

2. A process'for the manufactureof potassium 'formate 'c'onsi'siting' in mixing milk of lime with caustic lime and potassium sulphate in suchproportions and treating the same in the usual manner with carbon monoxide that the filtered solution contains 40 to potassium formate andjrespectively 60 to "30% calcium formate, causing this solution to react with sulphate'of potassium s'oas toform synge nite, separating the latter from the solution ofpotassium formate, treating'the same "with an aqueous solution of calcium' 'Iormate and separating the solution irom'the precipitated gypsum.

' 'EMIL'HENE. 

